Method of producing titanium alloys in powder form



United States Patent METHOD OF PRODUCING TITANIUM ALLOYS IN POWDER FORMDouglas W. Rostron, Haley, Ontario, and Harold A. Timm, Westrneath,Ontario, Canada, assignors to Dominion Magnesium Limited, Toronto,Ontario, Canada No Drawing. Application August 15, 1955, Serial No.528,536

9 Claims. (Cl. 75-.5)

This invention relates to the production of high purity titanium alloysin powder form directly from the oxide of titanium.

The present invention provides a direct method for the simultaneousreduction of titanium oxide and the alloying of the metal so formed withanother metal or metals, which latter may itself also be reduced fromits oxide or chloride during the operation. Without attaining themelting point of the desired alloy and with at least one of the mealsremaining in the solid state the metals alloy by diffusion with oneanother and are recovered in the form of powder. These prealloyedpowders can be melted much more readily and cast into homogeneousproducts than can mechanical mixtures of the individual metals whichconstitute the alloy powder. By this direct reduction and alloyingmethod alloy powders containing titanium and one or more other metalsare produced with greater ease and economy than by melting and alloyingthe individual metals.

In accordance with the invention an oxide of titanium is mixed with atleast one other metal or an oxide or chloride thereof, a reducing agentand a chloride of the reducing agents. The mixture is heated at atemperature below the fusion point of the alloy to be formed but abovethe melting point of the reducing agent, in an inert atmosphere toreduce the titanium oxide and the oxide or chloride of the metal to bealloyed, if such is used rather than the metal per se, and cause themetals to diffuse one within the other to form an alloy of such metalswithin the reaction mass.

In proceeding from titanium dioxide the method requires reduction in twostages. In the first stage magnesium in the form of minus 4 meshparticles is the reducing agent which is used in an amount at leastequal to 100 of the theoretical required to reduce the titanium oxideand alloying addition to at least 90% metal. Magnesium chloride in anamount of at least 40% by weight of the titanium dioxide plus oxides ofalloying elements present is added to the mixture as a fiux. Thisreaction is highly exothermic and the flux insures control of thereaction rate and peak temperatures during the reaction. This preventsformation of insoluble impurities such as titanates. The reaction massis cooled, broken up and leached with dilute hydrochloric acid to removemagnesium oxide, magnesium chloride and many unreacted magnesium.

This primary reaction product is mixed with alloying additions, minus 4mesh calcium particles in an amount at least 100% in excess of thestoichiometric requirement and calcium chloride as a flux in an amountof 10 to 150% by weight of the titanium oxide plus oxides of alloyingelements added. The product is then leached as in the first stage tofree the alloy powder from the reac tion by-products.

In each stage the reaction mixture is placed in a closed reactionvessel, which is evacuated and filled with an inert atmosphere of argonor the like and such atmosphere is maintained throughout the heatingoperation. In the first stage the mixture is heated at not less than1000 C. to reduce the titanium oxide and alloying additions to at leastmetal. In the second stage the mixture is heated to at least 1000 C. fora period of at least three hours after the reaction has been initiatedto insure complete reduction and alloying.

It is essential that the reaction products formed, during the reactingoperation, be readily removable from the mass by leaching in order thatthe alloy be recovered in the desired powder form. This is insured byuse of the oxides and chlorides as stated and more fully describedhereafter and no undesirable elements are introduced. When the reducingand alloying reactions are complete the mass is cooled. The dispersal ofthe soluble reaction products, including any unoxidized reducing agentand flux, within the mass leaves the cooled reaction product readilybroken up for leaching. Dilute hydrochloric acid is used as the solvent.

Aluminum and tin stabilize titanium in the alpha phase. Iron, manganese,chromium, molybdenum and vanadium stabilize titanium in the beta phase.

Whether the alloying addition is made as elemental metal, oxide orchloride, will depend on such factors as purity available, particle sizeand stability. Where metals are available in high purity powder formsuch as aluminum, iron and tin, they may be added as such. Addingalloying additions in the form of solid chlorides is preferred, sincethey introduce no oxygen and facilitate leaching. Where chlorideadditions are used, they may be substituted for at least part of theflux addition. When the alloying addition is not readily available inhigh purity metal powder form, or as a stable chloride, an oxide isused. The form of the alloying element selected must be free of impurityelements other than oxygen, hydrogen and chlorine, so as to minimize anyimpurity contamination of the final alloy from this source. Elementssuch as oxygen, hydrogen and chlorine can be tolerated, as they areconverted to a form during reaction that is readily separated from thealloy powder in subsequent processing.

Alloying additions are preferably introduced in the second reductionstage although when a high percentage of elements like vanadium andchromium are added as oxides that are difficult to reduce, it is best tomake at least part of the addition in the primary stage to insurecomplete reduction and a pure alloy powder. Alloying in the second stagereduces the tendency to form titanates because of lower reactiontemperatures and where compounds are used the heat generated by thereduction serves as a booster to effect complete reduction.

This method of direct reduction and alloying makes it possible toproduce alloys, having adequate physical and mechanical properties usingalloying additions which contain proportions of oxygen and likeimpurities which cannot be tolerated in the usual melting and alloyingmethods.

Because of the diffusion of the alloying metal into the titanium, duringthe direct reduction and alloying, the addition metal is more uniformlydispersed than when the metals are alloyed during melting by the usualmethods.

The diffusion of the alloying metal takes place while the titanium is inthe solid phase. When the reaction mass is leached the alloy remains inits finely divided form which is directly available for use by powdermetallurgy methods.

The following specific examples illustrate the method:

1. Alloying chromium with titanium.--A titanium oxide product containing93% titanium metal was mixed with 0.7 to 9.5% of its weight of chromicoxide, minus 4 mesh calcium particles to in excess of the stoichiometricrequirement and 10 to 150% by weight of the titanium oxide product pluschromic oxide of calcium chloride. The reactor containing this mixturewas heated Ultimate tensile-" ..p. s. i.-- 137,000

0.2% proof stress p. s. i. 126,200 Elongation percent 23.5 Reduction inarea do 57 2. Alloying manganese with titanium.A titanium X- ide productcontaining 93% titanium metal was mixed with 1.0 to 21.4% of its weightof manganese chloride, minus 4 mesh calcium particles 100 to 150% inexcess of the stoichiometric requirements and to 150% by weight of thetitanium oxide product plus managanesc chloride of calcium chlorideflux. The charge was heated in a reduction vessel as described inExample 1 and the product leached in the same manner.

Aluminum may be incorporated in this alloy by adding aluminum powder tothe initial charge in any desired amount. The preferred proportions are0.9 to 7.5% by weight of the titanium oxide product.

3. Alloying aluminum and vanadium with titanium.- A titanium oxideproduct containing 93% titanium metal was mixed with 0.9 to 10% of itsweight of vanadium pentoxide together with calcium reducing agent andcalcium chloride flux as in the previous examples. The reaction vesselwas heated at 1125 C. and the heating continued until the reduction andalloying were complete. The reaction mass was then cooled and leached asin the previous examples.

Aluminum may be incorporated in this alloy by adding aluminum powder tothe initial charge in any desired amount.

4. Alloying tin with titanium.A titanium oxide prod uct containing 93%titanium metal was mixed with 0.9 to 3.75% of its weight of tin powdertogether with calcium reducing agent and calcium chloride flux as in thepreceding examples. The reaction vessel was heated at 1000 C. until thereaction was complete. The cooled product was then leached with dilutehydrochloric acid to free the alloy powder.

Aluminum may be incorporated in this alloy by adding aluminum powder tothe initial charge.

5. Alloying chromium with titanium.-A titanium oxide product containing63% titanium metal was mixed with 0.4 to 6.1% of its Weight of chromicoxide, minus 4 mesh magnesium particles in an amount 25% in excess ofthe theoretical and magnesium chloride in amount equal to 50% by weighof the titanium oxide product plus chromic oxide. The charged reactionvessel was heated at 1000 C. for four hours to complete the reaction.The cooled reaction product was leached with dilute hydro chloric acidto free the alloy powder. This primary prodnot is used in the secondstage reaction as described in the previous examples.

Alloys produced by the method described have physical and mechanicalproperties superior to those of the same alloys produced by knownmethods.

This application is a continuation-in-part of application S. N. 439,874filed June 28, 1954, now abandoned.

What is claimed is:

1. A method of producing titanium alloys which comprises forming amixture of titanium oxide containing not less than 90% metal, a'nalloying addition being at least one of a group consisting of a titaniumphase stabi'lizing metal, its chloride and its oxide, minus 4 meshcalcium particles in an amount 100% in excess of the stoichiometricrequirement and calcium chloride 10 to 150% by weight of the titaniumoxide plus oxide of alloying addition, heating the mixture in an inertatmosphere at a temperature not substantially less than 1000 C. toeffect reduction and alloying of the metals, leaching the reaction masswith dilute hydrochloric acid and separating the titanium alloy powder.

2. A method of producing titanium alloys which comprises forming amixture of titanium oxide containing not less than titanium metal, 0.7to 9.5% of its weight of chromic oxide, minus 4 mesh calcium particlesat least by weight in excess of the stoichiometric and calcium chloride10 to by weight of the titanium oxide plus chromic oxide, heating themixture in an atmosphere at a temperature not substantially less than1000 C. to eflect reduction of the oxides and alloying of the metals,leaching the reaction mass with dilute hydrochloric acid and separatingthe alloy powder.

3. The method defined in claim 2 wherein 0.7 to 4.2% by weight of thetitanium oxide of molybdic oxide is incorporated in the charge. I

4. A method of producing titanium alloys which comprises forming amixture of titanium oxide containing not less than 90% titanium metal,1.0 to 21.4% of its weight of manganese chloride, minus 4 mesh calciumparticles at least 100% by weight in excess of the stoichiometric andcalcium chloride 10 to 150% by weight of the titanium oxide plusmanganese chloride, heating the mixture in an inert atmosphere at atemperature not substantially less than 1000 C. to eifect reduction ofthe titanium oxide and the manganese chloride and alloying of themetals, leaching the reaction mass with dilute hydrochloric acid andseparating the alloy powder.

5. A method of producing titanium alloys which comprises forming amixture of titanium oxide containing not less than 90% titanium metal,0.9 to 3.75% of its weight of tin in finely divided forrn, minus 4 meshcalcium particles at least 100% by weight in excess of thestoichiometric and calcium chloride 10 to 150% by weight of the titaniumoxide, heating the mixture in an inert atmosphere at a temperature notsubstantially less than 1000 C. to efiectreduction of the titanium oxideand diffusion of the tin in the titanium, leaching the reaction masswith dilute hydrochloric acid and separating the alloy powder.

6. A method of producing titanium alloys which comprises forming amixture of titanium oxide containing not less than 90% titanium metal,0.9 to 7.5% of its weight of aluminum in finely divided form, minus 4mesh calcium particles at least 100% by weight in excess of thestoichiometric and calcium chloride 10 to 150% by weight of 'thetitanium oxide, heating the mixture in an inert atmosphere at atemperature not substantially less than 1000' C. to effect reduction ofthe titanium oxide and diffusion of the aluminum in the titanium,leaching the reaction 'mass with dilute hydrochloric acid and separatingthe alloy powder.

7. A method of producing titanium alloys which com prises forming amixture of titanium oxide containing not less than 90% titanium metal,0.9 to 10% of its weight of vanadium pentoxide, minus 4 mesh calciumparticles at least 100% by weight in excess of the stoichiometric andcalcium chloride 10 to 150% by weight of the titanium oxide plusvanadium oxide, heating the mix ture in an inert atmosphere at atemperature not substantially less than 1000 C. to effect reduction ofthe titanium oxide and vanadium oxide and alloying of the metals,leaching the reaction mass with dilute hydrochloric acid and separatingthe alloy powder.

8. A method of producing titanium alloys which comprises forming amixture of titanium oxide with one of a group of alloying metalsconsisting of aluminum, tin, iron, manganese, chromium, molybdenum andvanadium, its oxideand chloride, minus 4 mesh particles of magnesium inan amount at least 100% of the theoretical requirement and withmagnesium chloridelin an amount at least 40% by weight of the titaniumoxide plus oxide of the alloying metal, heating the mixture in an inertatmosphere at 1000" C. to efiect partial reduction of the metals to forman alloy powder containing not more than 10% of combined oxygen, coolingthe reaction product crushing, leaching it with dilute hydrochloric acidto dissolve unreacted magnesium, magnesium oxide and magnesium chloride,separating the alloy powder from the solution and drying it,

9. The method defined in claim 8 wherein the alloy powder is mixed withminus 4 mesh calcium particles and with calcium chloride as a flux,heating the mixture in a reaction zone filled with inert gas, continuingthe heating at a temperature of at least 1000' C. until the titanium Ioxide and alloying addition have been reduced to metal and alloyed,cooling, crushing and leaching the reaction mass in. dilute hydrochloricacid to dissolve unreacted calcium, calcium oxide and calcium chloride,separating the alloy powder from the solution and drying it.

References Cited in the file of this patent UNITED STATES PATENTS OTHERREFERENCES Titanium, Report of Symposium on Titanium. Sponsored by theOflice of Naval Research, December 16, 1948. Pages 20 and 21.

1. A METHOD OF PRODUCING TITANIUM ALLOYS WHICH COMPRISES FORMING AMIXTURE OF TITANIUM OXIDE CONTAINING NOT LESS THAN 90% METAL, ANALLOYING ADDITION BEING AT LEAST ONE OF A GROUP CONSISTING OF A TITANIUMPHASE STABILIZING METAL, ITS CHLORIDE AND ITS OXIDE, MINUS 4 MESHCALCIUM PARTICLES IN AN AMOUNT 100% IN EXCESS OF THE STOICHIOMETRICREQUIREMENT AND CALCIUM CHLORIDE 10 TO 150% BY WEIGHT OF THE TITANIUMOXIDE PLUS OXIDE OF ALLOYING ADDITION, HEATING THE MIXTURE IN AN INERTATMOSPHERE AT A TEMPERATURE NOT SUBSTANTIALLY LESS THAN 1000*C. TOEFFECT REDUCTION AND ALLOYING OF THE METALS, LEACHING THE REACTION MASSWITH DILUTE HYDROCHLORIC ACID AND SEPARATING THE TITANIUM ALLOY POWDER.